1. Field of the Invention
The invention is directed generally to an apparatus for contactless energy and data transmission, having an immobile part (microstation) and a mobile part (microunit), for example a read/write station and a chip card.
2. Description of Prior Art
An apparatus for contactless energy and data transmission for a microstation and microunit employed in contactless chip cards or other data carriers such as electronic keys and modules is disclosed by German reference DE 34 47 560 C2, which was the priority basis for U.S. Pat. No. 4,697,183 issued to assignee herein. This reference discloses a two-coil transformer apparatus for a microstation that has bidirectional data transmission by 180.degree. phase modulation of one of the phases, linked with an amplitude modulation. German reference DE 34 47 560 C2 further discloses the apparatus of the microunit which works similarly with two transformer coils. German reference DE 36 14 477 C2, which was the priority basis for U.S. Pat. No. 4,796,028 issued to assignee herein, further discloses contactless energy and data transmission which requires only one transformer coil in the microstation and one in the microunit, and data recovery in this microunit is more complicated than that in German reference DE 34 47 560 C2. An additional capability of a microunit, similar to that disclosed in German reference DE 36 14 477 C2, is that it can also be operated at an increased distance from a microstation by using a large format coil in the microunit.
A common problem of existing card readers is that faults are caused by improper insertion of the card into the card reader. A card reader is needed for providing fault-free, contactless data transmission when the card is in a multitude of orientations.